Uncertainty Evaluation of a 10 V RMS Sampling Measurement System Using the AC Programmable Josephson Voltage Standard

We have evaluated the uncertainty in the differential sampling measurement of the RMS amplitude of 10 V waveform synthesis based on an AC programmable Josephson voltage standard system with a compact cooler and a modified digital voltmeter (DVM). The error due to a sampling DVM timer is much reduced with an external 20-MHz frequency reference for the sampling DVM. The thermal electromotive force voltage of our reverse-polarity relay switch is sufficiently small and stable for the application of a differential sampling system. We have also performed a variety of measurements to evaluate this differential sampling technique. The evaluation results show that the overall expanded uncertainty is 1.3 parts in 10⁶ (k = 2) for the frequency of 62.5 Hz at an rms amplitude of 10 V.